Radio base station apparatus

ABSTRACT

A transmission weight computing section computes a transmission weight for directional transmission using an OFDM signal. A transmission correcting value memory section stores one correcting value for correcting the transmission weight for each sub-carrier of an OFDM signal or each band gathering a plurality of sub-carriers. A transmission weight correcting section corrects the transmission weight by the correcting value. A transmitting branch weights transmission data by a transmission weight outputted from the transmission weight correcting section on a sub-carrier-by-sub-carrier basis and delivers it to an antenna.

TECHNICAL FIELD

This invention-relates to a radio base-station apparatus of a radiocommunications system using an orthogonal frequency dividing multiplex(hereinafter referred to as “OFDM”) scheme, and more particularly to adirectional transceiver apparatus using an array antenna.

BACKGROUND ART

Conventionally, there is a communication scheme using OFDM broadly knownas the radio base-station apparatus. Meanwhile, adaptive array antennatechnology is now under study aiming at increasing the traffic capacity,broadening the communications area, suppressing the interference and thelike. Attentions are drawn to the applications of the adaptive arrayantenna technology of the OFDM scheme. For example, there are those,including a description in JP-A-11-205026. This publication describesthat a transmission/reception weight is computed on the basis of aninterval of OFDM sub-carrier frequencies and an interval ofarray-antenna elements, so that weighting is carried out based on eachsub-carrier thereby implementing directional transmission/reception.

In this conventional art, by setting transmission and reception weightsfor each sub-carrier, it is possible to eliminate the deviation ofdirectional beam pattern that occurs at the interval of sub-carrierfrequencies. However, where amplitude or phase deviation takes place atbetween transmitting/receiving branches, the formed beam pattern woulddeviate from the desired beam pattern. The radio-frequency circuitsection, as, a constituent element of each transmitting/receivingbranch, is configured with many analog elements. These analog elementscause a characteristic deviation because of the difference betweenindividual elements. Furthermore, the characteristic is varied bysurrounding temperature, lapsing time and so on. By such analog elementcharacteristic, amplitude/phase deviation is caused between thetransmitting/receiving branches. Particularly, it is considered that, ona broadband signal such as an OFDM signal, a frequency characteristic iscaused in the amplitude/phase deviation between the branches. Meanwhile,on the lines up to the antenna element, there occurs a difference indelay time between the transmitting branches because of the differenceof line length to the antennas or line characteristic. From thesefactors, the amplitude/phase relationship set in transmission weightreadily collapses between the antenna elements, making it impossible toobtain an ideal beam pattern. Meanwhile, there is a drawback that, inthe case a broadband signal is sent, a different pattern of beam ispossibly formed based on the frequency resulting from a deviatedfrequency characteristic.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a radio base-stationapparatus which can form a desired directional beam pattern even in thecase that an amplitude/phase deviation occurs between the branches of anarray antenna, particularly when there is a frequency characteristic onthe amplitude/phase deviation.

The radio base-station apparatus of the invention previously storescorrecting values, based on each sub-carrier of OFDM signal, forcorrecting a characteristic of a radio circuit section in eachtransmitting/receiving branch of an array antenna. By correcting acomputed transmission/reception weight with using a correcting value, adesired transmitting/receiving beam pattern is formed.

Meanwhile, the radio base station of the invention detects anamplitude/phase deviation between branches caused from a characteristicvariation of the radio circuit sections in the respectivetransmitting/receiving branches of an array antenna, and stores acorrecting value for correcting that deviation. Thereupon, detection ismade based on each sub-carrier of OFDM signal, to compute a correctingvalue. Using the correcting value, the transmitting/receiving weight iscorrected to weight the signal. Due to this, even where there is anamplitude/phase deviation between the branches, a desired beam patterncan be formed thereby enabling favorable communications.

A radio base-station apparatus of the invention comprises: atransmission weight computing section for computing a transmissionweight for directional transmission using an OFDM signal; a transmissioncorrecting value memory section for storing one correcting value forcorrecting the transmission weight for each sub-carrier of an OFDMsignal or each band gathering a plurality of sub-carriers; atransmission weight correcting section for correcting the transmissionweight by the correcting value; and a transmitting branch for weightingtransmission data with a transmission weight outputted from thetransmission weight correcting section on a sub-carrier-by-sub-carrierbasis and deliver it to an antenna element. Due to this, whendirectionally transmitting an OFDM signal, the transmitting weight canbe corrected by a correcting value, to form a transmission beam.

Meanwhile, a radio base-station apparatus of the invention comprises aplurality of the transmitting branches and an array antenna structuredby a plurality of the antenna elements. Due to this, when directionallytransmitting an OFDM signal by using an array antenna, the transmittingweight can be corrected by a correcting value, to form a transmissionbeam.

Meanwhile, the transmitting branch of a radio base-station apparatus ofthe invention comprises a weight operating section for weighting thetransmission data with a transmission weight outputted from thetransmission weight correcting section, an inverse fast Fouriertransform operating section for carrying out inverse Fouriertransformation on an output signal of the weight operating section, aD/A converting section for converting an output signal of the inversefast Fourier operating section into an analog signal, and atransmitting-system radio circuit section for frequency-converting anoutput signal of the D/A converting section into a radio frequency. Dueto this, an OFDM signal with a transmitting weight can be fed to theantenna element.

Meanwhile, the transmission weight correcting section of a radiobase-station apparatus of the invention corrects, based on eachsub-carrier or based on each band gathering together a plurality ofsub-carriers, an OFDM-signal-sub-carrier based transmission weightcomputed in the transmission weight computing section, by using acorrecting value stored in the transmission correcting value memorysection. Due to this, a desired beam pattern can be formed moreaccurately within a bandwidth of OFDM signal.

Meanwhile, the transmission weight computing section of a radiobase-station apparatus of the invention divides an OFDM signal bandwidthinto a plurality and computes one transmission weight for a plurality ofsub-carriers existing in a divisional band, the transmission weightcorrecting section correcting, based on each sub-carrier or based oneach band gathering together a plurality of sub-carriers, a transmissionweight computed in the transmission weight computing section by using acorrecting value stored in the transmission correcting value memorysection. Due to this, a desired beam pattern can be formed moreaccurately within a bandwidth of OFDM signal while reducing the numberof times of transmitting weight computations.

Meanwhile, the correcting value stored by the transmission correctingvalue memory section of a radio base-station apparatus of the inventionis to correct an amplitude deviation and phase deviation to occurbetween the transmission branches. Due to this, the storage capacity ofthe transmission correcting memory section can be efficiently reduced.

Meanwhile, the weight operating section of a radio base-stationapparatus of the invention weights transmission data on asub-carrier-by-sub-carrier basis, with a transmission weight of eachsub-carrier corrected by the transmission weight correcting section. Dueto this, a desired beam pattern can be formed more correctly becauseweighting is possible based on each sub-carrier of OFDM signal.

Meanwhile, a radio base-station apparatus of the invention furthercomprises a correcting branch radio circuit section for inputting asignal outputted from the transmitting branch and carrying out at leastfrequency conversion, an A/D converting section for converting an outputsignal of the correcting branch radio circuit section into a digitalsignal, a fast Fourier transform operating section forFourier-transforming an output digital signal of the A/D convertingsection, and a frequency-response correcting value detecting section fortaking as a reference an output signal of the weight operating section,to detect an amplitude deviation and phase deviation of a signal of fromthe fast Fourier operating section and detect a correcting value forcorrecting an amplitude deviation and phase deviation between thetransmitting branches, the antenna element being removable. Due to this,the antenna element can be easily removed, to use the correcting branchfor detecting an amplitude and phase deviation between the transmittingbranches and computing and storing a correcting value.

Meanwhile, the transmission correcting value memory section of a radiobase-station apparatus of the invention is stored with a correctingvalue computed by the frequency-response correcting value detectingsection when the correcting branch radio circuit section is connected,one to one, with the transmitting branch in a state the antenna elementis not connected. Due to this, in the transmission correcting valuememory section, actually measured correct one can be stored as acorrecting value to an amplitude and phase deviation betweentransmitting branches.

Meanwhile, a radio base-station apparatus of the invention furthercomprises power distributing section arranged close to the antennaelement, a correcting branch radio circuit section for inputting asignal distributed in the power distributing section and carrying out atleast frequency conversion, an A/D converting section for converting anoutput signal of the plurality of correcting branch radio circuitsections into a digital signal, a fast Fourier transform operatingsection for Fourier-transforming an output digital signal of the A/Dconverter section, and a frequency-response correction detecting sectionfor taking as a reference an output signal of the weight operatingsection, to detect an amplitude deviation and phase deviation of asignal of from the fast Fourier transform operating section and detect acorrecting value for correcting an amplitude deviation and phasedeviation between the transmitting branches, the transmission correctingvalue memory section being stored with a correcting value detected bythe frequency-response correction detecting section. Due to this, it ispossible to detect a correcting value for correcting an amplitude andphase deviation between transmitting branches, at any time duringtransmission.

Meanwhile, the frequency-response correction detecting section of aradio base-station apparatus of the invention detects an amplitude andphase of an output signal of the fast Fourier transform operatingsection based on each sub-carrier of OFDM signal, and detects acorrecting value for correcting an amplitude deviation and phasedeviation between transmitting branches on a sub-carrier-by-sub-carrierbasis by using a detection result of the amplitude and phase. Due tothis, it is possible to obtain a correction value for forming morecorrectly a desired beam pattern within an OFDM signal bandwidth.

Meanwhile, a radio base-station apparatus of the invention furthercomprises a first switch for selecting one from signals distributed by aplurality of power distributing section and connecting it with thecorrecting branch radio circuit section, and a second switch forselecting a signal from a plurality of weight operating sections andconnecting it with the frequency-response correcting value detectingsection, the first switch and the second switch selecting the signalfrom the same transmitting branch. Due to this, even in case thecorrecting branch is one in the number, switching the both switchesenables to determine a correcting value to an amplitude and phasedeviation on all the transmitting branches.

Meanwhile, a radio base-station apparatus of the invention furthercomprises a transmission correcting matrix memory section previouslystoring a correcting matrix for correcting a coupling between antennaelements, the transmission weight correcting section further correctingthe transmission weight by the correcting matrix. Due to this, thecoupling between antenna elements can be corrected in addition to thecorrection to an amplitude and phase deviation between transmittingbranches.

Meanwhile, the transmission correcting matrix memory section of theradio base-station apparatus of the invention is stored with correctingmatrixes based on each sub-carrier of OFDM signal. Due to this, it ispossible to correct a coupling between antenna elements based on eachsub-carrier of OFDM signal.

Meanwhile, the transmission correcting matrix memory section of a radiobase-station apparatus of the invention is stored with correctingmatrixes based on a plurality of sub-carrier existing in plurallydevided signal bands of OFDM signal. Due to this, the storage capacityof the transmitting correcting matrix memory section can be reduced bycorrecting a coupling between antenna elements based on each divisionalband in an OFDM signal bandwidth.

Meanwhile, a radio base-station apparatus of the invention comprises: areception weight computing section for computing a reception weight byusing a plurality of demodulated signal that an OFDM signal received atan array antenna is demodulated; a reception correcting value memorysection for storing one correcting value for correcting the receptionweight for each sub-carrier of an OFDM signal or each band gathering aplurality of sub-carriers; a reception weight correcting section forcorrecting the reception weight by the correcting value; and a weightoperating section for weighting the demodulated signal with thecorrected reception weight. Due to this, in the case of directionallyreceiving an OFDM signal by using an array antenna, a reception beam canbe formed by correcting a reception weight with a correcting value.

Meanwhile, the reception weight correcting section of a radiobase-station apparatus of the invention corrects, based on eachsub-carrier or based on each band gathering together a plurality ofsub-carriers, an OFDM-signal-sub-carrier based reception weight computedin the reception weight computing section, by using a correcting valuestored in the reception correcting value memory section. Due to this, inthe case of directionally receiving an OFDM signal by using an arrayantenna, a reception beam can be correctly formed by a correction on asub-carrier-by-sub-carrier basis.

Meanwhile, the reception weight computing section of a radiobase-station apparatus of the invention divides an OFDM signal bandwidthinto a plurality and computes one reception weight for a plurality ofsub-carriers existing in a divisional band, the reception weightcorrecting section correcting, based on each sub-carrier or based oneach band gathering together a plurality of sub-carriers, a receptionweight computed in the reception weight computing section by using acorrecting value stored in the reception correcting value memorysection. Due to this, in the case of directionally receiving an OFDMsignal by using an array antenna, a reception beam can be nearlycorrectly formed while reducing the number of times of reception weightcomputations.

Next, the correcting value stored in the reception correcting valuememory section of a radio base-station apparatus of the invention is tocorrect an amplitude deviation and phase deviation to occur between thereceiving branches. Due to this, in the case of directionally receivingan OFDM signal by using an array antenna, it is possible to store asub-carrier-based correcting value for forming a reception beam morecorrectly.

Meanwhile, the weight operating section of a radio base-stationapparatus of the invention weights the demodulated signal, based on eachsub-carrier, by a reception weight of each sub-carrier corrected by thereception weight correcting section. Due to this, in the case ofdirectionally receiving an OFDM signal by using an array antenna, areception beam can be formed more correctly by the weighting correctedbased on each sub-carrier.

Meanwhile, a radio base-station apparatus of the invention comprises: areference signal generating section for generating a signal as areference to detect an amplitude deviation and phase deviation betweenreceiving branches; an inverse fast Fourier transform operating sectionfor Fourier-transforming a signal of from the reference signalgenerating section; a D/A converting section for converting an outputsignal of the inverse fast Fourier operating section into an analogsignal; a correcting branch radio circuit section forfrequency-converting the output analog signal of the D/A convertingsection into a radio frequency; and a frequency-response correctingvalue detecting section for taking as a reference an output signal ofthe reference signal generating section, to detect an amplitudedeviation and phase deviation of an output signal of from the fastFourier operating section and detect a correcting value for correctingan amplitude deviation and phase deviation between the receivingbranches, the array antenna being removable. Due to this, a correctingbranch can be used in detecting an amplitude and phase deviation betweenreceiving branches and in computing and storing a correcting value.

Meanwhile, the reception correcting value memory section of a radiobase-station apparatus of the invention stores a correcting valuecomputed by the frequency-response correcting value detecting sectionwhen the correcting branch radio circuit section is connected, one toone, with the receiving branch in a state the antenna element is notconnected. Due to this, in the reception correcting value memorysection, actually measured correct one can be stored as a correctingvalue to an amplitude and phase deviation between receiving branches.

Meanwhile, a radio base-station apparatus of the invention comprises: areceiving circuit section having a receiving weight computing sectionfor computing a reception weight by using a plurality of demodulatedsignals that an OFDM signal received at an antenna element configuringan array antenna is demodulated; a reception correcting value memorysection storing a correction value for correcting the reception weightbased on each sub-carrier of OFDM signal or based on band gatheringtogether a plurality of sub-carriers; a reception weight correctingsection for correcting the reception weight by the correcting value; anda weight operating section for weighting the demodulated signal by thecorrected reception weight; a transmitting circuit section having atransmission weight computing section for computing a transmissionweight for directional transmission by using information about adirectivity in the reception weight computing section; a transmissioncorrecting value memory section for storing a correction value forcorrecting the transmission weight based on each sub-carrier of OFDMsignal or based on band gathering together a plurality of sub-carriers;a transmission weight correcting section for correcting the transmissionweight by the correcting value; and a transmitting branch for weightingtransmission data by a transmission weight outputted from thetransmission weight correcting section on a sub-carrier-by-sub-carrierbasis and delivering it to the antenna element; and a switch section forswitching over a connection between the antenna element and thereceiving circuit section or a connection between the antenna elementand the transmitting circuit section. Due to this, in the case ofdirectionally transmitting and receiving an OFDM signal by using anarray antenna, the transmission and reception weight can be corrected bya correcting value, to form a transmission and reception beam.

As in the above, according to the present invention, in the transmitterapparatus for directionally transmitting an OFDM signal by using anarray antenna, a correction value detected on asub-carrier-by-sub-carrier basis is held for an amplitude/phasedeviation to occur between the transmitting branches, enabling tocorrect the transmission weight on a sub-carrier-by-sub-carrier basis.Due to this, it is possible to put, near a desired beam pattern, adeviation of beam pattern occurring due to an amplitude/phase deviationbetween the transmitting branches and a frequency characteristic of thedeviation. Furthermore, by detecting a correcting matrix for correctinga coupling between antenna elements on a sub-carrier-by-sub-carrierbasis, it is possible to correct a coupling between antenna elements onthe basis of each carrier within a signal bandwidth. From these, adesired beam pattern can be obtained even on a broadband signal,obtaining favorable communications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block connection diagram of a radio base-station apparatusaccording to embodiment 1 of the invention.

FIG. 2 is a concept view of assigning a reception weight for an OFDMsignal in embodiment 1.

FIG. 3 is an operation concept diagram of a weight operating section inembodiment 1.

FIG. 4 is a block connection diagram exemplifying a correcting-valuedetecting method in embodiment 1.

FIG. 5 is a block connection diagram of a radio base-station apparatusaccording to embodiment 2.

FIG. 6 is a block connection diagram of a radio base-station apparatusaccording to embodiment 3.

FIG. 7 is a block connection diagram of a radio base-station apparatusaccording to embodiment 4.

FIG. 8 is a block connection diagram of a radio base-station apparatusaccording to embodiment 5.

FIG. 9 is a block connection diagram exemplifying a correcting-valuedetecting method in embodiment 5.

FIG. 10 is a block connection diagram of a radio base-station apparatusaccording to embodiment 6.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention are explained by using thedrawings.

(Embodiment 1)

FIG. 1 is a block connection diagram of a radio base station apparatusaccording to a first embodiment of the present invention The radio basestation apparatus is an apparatus to send a signal of an OFDM modulationscheme, and has an array antenna made up by a plurality of antennaelements. A weight operating section 102 controls the amplitude andphase of a signal radiated at antenna elements, thereby enablingdirectional sending of signals.

In FIG. 1, a transmission branch 101-1, 101-2, . . . 101-N is configuredwith a weight operating section 102-1, 102-2, . . . 102-N, an inversefast Fourier transform (IFFT) operating section 103-1, 103-2, . . .103-N, a digital/analog (D/A) converting section 104-1, 104-2, . . .104-N, and a transmission-system radio circuit section 105-1, 105-2, . .. 105-N. Herein, provided that the number of antenna elements is N, thetransmission branch are N systems in the number.

The array antenna is made up by a plurality of antenna elements 106-1,106-2, . . . 106-N. These antenna elements are removably arranged.

A transmitting-data generating section 100 generates information to besent, and outputs a transmitting-data string St1. Generally, thetransmitting-data string St1 is in a radio access channel configurationprocessed by coding, multiplexing or the like. For example, theFrequency Division Multiple Access scheme (FDMA) is to implementmultiplex within a frequency domain, the Time Division Multiple Accessscheme (TDMA) is to carry out multiplex within the time domain, and theCode Division Multiple Access scheme (CDMA) is to perform codemultiplex. Herein, there is no need to especially limit thetransmitting-data generating section 100 and transmitting-data stringSt1 to such a signal format. For example, the transmitting-data stringSt1 may be a complex-numbered data string, comprising a common-modecomponent (I channel) and an orthogonal component (Q channel). Atransmission-weight computing section 111 computes a transmission-weightWt1 to control the amplitude and phase of a transmitting signal forradiation through the antenna elements.

Generally, the transmission weight is complex-number data capable ofrepresenting an amplitude and phase. Although there are some techniquesas methods to compute a transmission weight Wt1, the transmission-weightcomputing section 111 does not require for the technique to be limittedespecially. Herein, as one example of a method to compute a transmissionweight, there is a method of estimating a direction of mobile station onthe basis of a signal from a mobile station received in a base station.

The transmission-weight computing section 111 computes a transmissionweight such that a beam pattern has a directivity directed toward thedirection to mobile station thus obtained.

Herein, because the transmitting signal is an OFDM signal, itssub-carriers can be set by transmission weights. As shown in FIG. 2,where taking a transmitting method to set a transmission weight on asub-carrier-by-sub-carrier basis, an optimal transmission weight can beset for each sub-carrier by computing a transmission weightindependently of each sub-carrier. In FIG. 2, n represents a sub-carriernumber. In computing a transmission weight in this case, there is a needfor frequency of each sub-carrier and an interval of the array antennatherefor. In case the number of all the sub-carriers of OFDM signal isassumed F, F times computation processes are required in computing allthe transmission weights based on each sub-carrier requires (201).

Meanwhile, as shown in FIG. 2, the OFDM signal domain can be dividedinto a plurality of bands so that the sub-carriers existing in the bandare set, as one group, with the same transmission weight (202). In thiscase, m represents the number of divisional bands. The frequencyrequired in computing a transmission weight desirably uses a centerfrequency of a band as a subject-of-computation. In the case the OFDMsignal band is divided into M, M times of computation processes arerequired to compute all the transmission weights. However, operationamount can be reduced as compared with the case of setting atransmission weight for each sub-carrier. This is effective particularlyin such broadband communications as to use the band up to 100 MHz.Meanwhile, in the case of dividing the OFDM signal band, division may beat an equal interval or at an unequal interval. This is because, wherethe frequency characteristic of amplitude/phase deviation is not evenover the entire band, band division is preferably made with deviationsin an equal degree. In the case that amplitude/phase deviation occursgreatly at or around the band both ends relative to the deviation at theband center, band division is especially fine at or around the band bothends. Furthermore, sole one transmission weight can be set to all thesub-carriers. In this case, the process is only once in computingtransmission weights. The transmission weight Wt1 thus computed isoutputted.

A transmission correcting-value memory section 112 stores a correctingvalue Ct for correcting an amplitude deviation and phase deviation tooccur between the transmitting branches 101. In the case thetransmitting signal has a broad signal band, the amplitude deviation andphase deviation occurred at between the transmitting branches 101 has afrequency characteristic. With the OFDM signal, such a frequencycharacteristic in amplitude and phase deviation can be corrected on asub-carrier-by-sub-carrier basis. Consequently, the transmissioncorrecting-value memory section 112 is previously stored withsub-carrier-based correcting values for the transmitting branches.Namely, provided that the number of transmitting branches is N and thenumber of all the sub-carriers is F, correcting values in the number of(N×F) are stored.

Meanwhile, the transmission correcting-value memory section 112 candivide a signal band into a plurality similarly to the transmissionweight computing section 111, to store correcting values Ct in thenumber of divisional bands. Also, only one correcting value Ct can bestored for the entire signal band.

Explained later is a method to determine a correcting value C forcorrecting the amplitude and phase deviation between the transmittingbranches 101. Herein, there is, as a data form of correcting value Ct,complex-number data for representing an amplitude and phase.

A transmission weight correcting section 113 makes a correction on thetransmission weight Wt1 computed in the transmission weight computingsection 111 by a correcting value Ct stored in the transmissioncorrecting-value memory section 112. Where the transmission weight Wt1and the correcting value Ct are both complex-number data, correction ispossible by means of a complex multiplication of transmission weight Wt1and correcting value Ct. Herein, shown in the following, as one example,is a corrected transmission weight Wt2 to be outputted from thetransmission weight correcting section 113 in the case that thetransmission weight Wt1 is computed based on each sub-carrier andsimilarly the correcting value Ct is stored based on each sub-carrier.Wt2_(−n)(f)=Wt1_(−n)(f)·Ct _(−n)(f) where n=1, . . . ,N; f=1, . . . ,F

Herein, N is the number of array antenna elements while F represents thenumber of sub-carriers in the OFDM signal.

Now, explained is the operation in the transmitting branch 101. Herein,the transmission branches have the same function as to the weightoperating section 102, IFFT operating section 103, D/A convertingsection 104 and transmission-system radio circuit section 105configuring the transmitting branch. Accordingly, the operation isexplained representatively on the N-th transmitting branch.

In the outset, the transmitting data St1 outputted from the transmittingdata generating section 100, in the weight operating section 102-N, isweighted based on a transmission weight Wt outputted from thetransmission weight correcting section 113. When the transmitting dataSt1 and the transmission weight Wt2 are respectively complex-numberdata, weight operation is possible by complex multiplication. Herein,using FIG. 3, outlined is an operation of the weight operating section102 in the case transmission weights Wt2 are set based on eachsub-carrier of OFDM signal. FIG. 3 is an operation concept view of theweight operating section. In FIG. 3, transmitting data St1 ischronological data. In the case of setting a transmission weight basedon each sub-carrier of OFDM signal, the transmitting data St1 istransformed based on each sub-carrier and multiplied by transmissionweights based on each sub-carrier, thereby enabling weighting. In orderto realize this, a first series/parallel (S/P) transforming section102-A transforms time-series transmitting data St1 into thecorresponding parallel transmitting data on thesub-carrier-by-sub-carrier basis. A second series/parallel (S/P)transforming section 102-B transforms a time-series transmission weightWt2 into sub-carrier-based parallel transmitting data. Multipliers 102-Cmultiply the parallel transmitting data St1 by a transmission weightWt2, on a sub-carrier-by-sib-carrier basis. Each multiplier has outputdata S2 that can be expressed as follows:St 2(f)=St 1(f)·Wt 2(f) where f=1, . . . ,F

Herein, f represents a sub-carrier number. Meanwhile, becausetransmitting data St1 and transmission weight Wt2 are generallycomplex-number data, complex multiplication is carried out in themultiplier 102-C. Accordingly, the weight operating section 102 outputsa sub-carrier-based output signal St2. Incidentally, although the FIG. 3example is configured to transform the input transmitting data St1 intoparallel data based on the sub-carrier basis, this is not particularlylimited to. Realization is possible in case the configuration is for aconvoluting operation capable of weighting with a sub-carrier-basedtransmission weight while keeping the transmitting data St1 aschronological data.

Then, the output data St2 of the weight operating section 102 isinversely Fourier-transformed by the IFFT operating section 103. Herein,although there is available discrete Fourier transformation as acomputation method for inverse Fourier transformation, inverse fastFourier transform (IFFT) is desirable in terms of computation time andoperation processing amount. Herein, omitted is the detailed explanationconcerning IFFT. Meanwhile, as shown in FIG. 3, in the case that theoutput data St2 of the weight operating section 102 is sub-carrier-basedparallel data, the IFFT operating section 103 carries out inverseFourier operation on the parallel data as it is. Otherwise, in the casethat the output data St2 is chronological data, series/parallel (S/P)transform is once made to have parallel data on which inverse Fouriertransformation is carried out. As a result of inverse Fouriertransformation, time-waveform transmitting data St3 is outputted.Time-waveform transmitting data St3 can be expressed as follows:St 3(t)=F ⁻¹ {St 2(f)} where St 3(f)=St 2(f)  (1)

Herein, F⁻¹ represents inverse Fourier transformation. From then on, thetransmitting signal is in a time-waveform but shown by a frequencywaveform. In the D/A converting section 104, the output time-waveformtransmitting data St3 from the IFFT operating section 103 is transformedfrom a digital signal into an analog signal. The output signal St4 ofthe D/A converting section 104 is an analog time-waveform transmittingsignal.

Then, the analog time-waveform transmitting signal St4, as an output ofthe D/A converting section 104, is frequency-converted from a base-bandfrequency into a radio frequency in the transmitting-system radiocircuit section 105. Thereafter, transmitting-signal process is carriedout in the radio frequency band, e.g. power amplification, in order forradiation through the antenna element. Incidentally, besides this, afilter process and the like are included in the transmitting-signalprocess. Thus, a radio transmitting signal St5, as an output signal ofthe transmitting-system radio circuit section 105, is radiated throughthe antenna terminal 106.

Now, explanation is made on a method for determining a correcting valueCt, referred before. The correcting value Ct is to detect a frequencycharacteristic of amplitude/phase deviation in the transmitting-signalcircuit section 105 and to correct a deviation thereof. Consequently,computing a correcting value Ct is satisfactorily to detect a frequencycharacteristic of amplitude/phase deviation in the transmitting-signalcircuit section 105. For example, there is the following method, whichis explained in the below by using FIG. 4.

FIG. 4 is the radio base-station apparatus of this embodiment with theremoval antenna elements removed and with a correcting branch forcomputing a correcting value connected. In FIG. 4, a correcting branch121 is configured with a correction-branch radio circuit section 122, anA/D converting section 123, and an FFT operating section 124. Herein,the correction-branch radio circuit section 122 is to frequency-converta radio frequency signal into a base-band frequency or intermediatefrequency. Besides these, processes such as filtering are included.Meanwhile, because of a configuration with many analog circuitssimilarly to the transmitting-system radio circuit section 105, afrequency characteristic takes place due to the analog-elementcharacteristic. This frequency characteristic is expressed as follows:Zc(f)

A frequency-response correcting value detecting section 114 is to detecta frequency characteristic of amplitude and phase deviation on a signalSct4 of from the correcting branch 121, on the basis of an output signalSt2 of the weight operating section 102 in the transmitting branch 102.The other configuration blocks are the same as those described in FIG.1, having the same function.

Herein, explanation is made on a method of detecting a correcting valuerelated to the N-th transmitting branch. As for the other transmittingbranches, a correction can be similarly detected by changing theconnection of the transmitting branch 101 and correcting branch 121 andthe connection of the weight operating section 102 andfrequency-response correcting value detecting section 114.

At first, the antenna element is removed, to connect thetransmitting-system radio circuit section 105-N to an input of thecorrecting branch 121. Herein, the frequency characteristic of amplitudeand phase variation in the transmitting-system radio circuit section 105is assumably expressed as follows:Z(f)  (2)

Using Equations (1) and (2), the transmitting signal St5 as an output ofthe transmitting-system radio circuit section 105 is changed as follows:$\begin{matrix}{{{St5}(f)} = {{{St2}(f)} \cdot {Z(f)}}} \\{= {{{St1}(f)} \cdot {{Wt1}(f)} \cdot {C(f)} \cdot {Z(f)}}}\end{matrix}$

For example, the transmitting signal St5-N in the n-t branch in thestate there is no correcting value, i.e. in the case of Ct=1, is asfollows:St 5−N(f)=St 1(f)·Wt1−N(f)·Z−N(f)  (3)

Due to this, the input signal Sct1 to the correcting branch 121 is atransmitting signal St5−N of the N-th transmitting branch. Accordingly,as shown in Equation (3), in the state there is no correcting value,i.e. in the case of C=1, we have the following:Sct 1(f)=St 5−N(f)=St 1(f)·Wt1−N(f)·Z−N(f)

The input signal Sct1 is a radio frequency signal, which is to befrequency-transformed in a correcting-branch radio circuit section 122.However, because of a frequency characteristic Zc(f) caused by thecorrecting-branch radio circuit section 122, the output signal Sct2 isgiven in the following equation.Sct 2(f)=Sct 1(f)−Zc(f)=St 1(f)·Wt1−N(f)−Z−N(f)·Zc(f)

Then, the output signal Sct, in the A/D converting section 123, isconverted into a digital signal Sct3. Herein, the clock for use in theA/D converting section 123 uses the same one as the D/A convertingsection 104 whereby the A/D converting section 123 can output a‘digital’ signal Sct3 same in sampling rate as and synchronous with thatof the D/A converting section 104.

Next, the FFT operating section 124 Fourier-transforms the digitalsignal Sct3 outputted from the A/D converting section 123, to outputfrequency waveform data Sct4. The frequency waveform data Sct4 isinputted to the frequency-response correcting value detecting section114.

On the other hand, the output signal St2−N of the weight operatingsection 102-N is inputted to the frequency-response correcting valuedetecting section 114, similarly to the frequency waveform data Sct4.

Then, in the frequency-response correcting value detecting section 114,detected is a frequency characteristic of amplitude and phase deviationof the signal Sct2 from the correcting branch 121 on the basis of theoutput signal St2 of the weight operating section in the transmittingbranch 102. Herein, provided that the frequency characteristic ofamplitude and phase deviation is h, there is, for example, the followingmethod as a detecting method: $\begin{matrix}{{{hN}(f)} = {{{Sct4}(f)} \cdot \left( {{St2} - {N(f)}} \right)^{*}}} \\{= {{St2} - {{N(f)} \cdot Z} - {{N(f)} \cdot {{Zc}(f)} \cdot \left( {{St2} - {N(f)}} \right)^{*}}}} \\{= {{{{{St2} - {N(f)}}}^{2} \cdot Z} - {{N(f)} \cdot {{Zc}(f)}}}} \\{= {Z - {{N(f)} \cdot {{Zc}(f)}}}}\end{matrix}$

From the frequency characteristic h of amplitude and phase deviationthus determined, the correcting value Ct can be determined as follows:$\begin{matrix}{{{Ct} - {N(f)}} = \frac{1}{{hN}(f)}} \\{= \frac{1}{Z - {{N(f)} \cdot {{Zc}(f)}}}}\end{matrix}$

In this manner, it is possible to detect a correcting value Ct−N forcorrecting the frequency characteristic of amplitude and phase deviationof the transmitting-system radio circuit section 105−N, in respect ofthe N-th transmitting branch 101−N.

The detected correcting value Ct−N is inputted to and stored in thetransmission correcting-value memory section 112, whereby it can be usedin correcting a transmission weight. Furthermore, by carrying out thecorrecting-value detecting operation for all the transmitting branches,the transmission correcting-value memory section 112 is allowed to storethe correcting values of all the branches and all the sub-carriers.

Incidentally, the correcting value Ct stored in the transmissioncorrecting-value memory section 112 includes a frequency characteristicZc of the correction-branch radio circuit section 122 of the correctingbranch 121. Because of common between all the branches, the relativerelationship is kept between the branches in each sub-carrier.Accordingly, this does not have an effect upon the transmission weight.However, by separately making a measurement as to only the correctingbranch 121 and detecting a frequency characteristic Zc of the correctingbranch radio circuit 122, the frequency characteristic Zc can be removedfrom the correcting value Ct.

As described above, according to the present embodiment, wheredirectionally sending a broadband OFDM signal, by correcting a frequencycharacteristic of amplitude and phase deviation to occur between thetransmitting branches on each sub-carrier, a desired beam pattern can beformed within an OFDM-signal bandwidth. This realizes efficienttransmission.

Incidentally, in the case that the radio base-station apparatus of thisembodiment is used in FDMA, the transmitting data generating section 100generates such a signal as to be frequency-multiplexed in order toassign a plurality of sub-carriers to the respective users. Meanwhile,the transmission weight computing section 111 generates a transmissionweight for each sub-carrier assigned to the user, correspondingly to thedata generated in the transmitting data generating section 100.

Incidentally, where the radio base-station apparatus of this embodimentis used in TDMA, the transmitting data generating section 100 generatesa signal time-multiplexed such that time is assigned based on each user.Meanwhile, the transmission weight computing section 111 makes aprocessing for each transmit weight correcting section 113 while theweight operating section 102 carries out processing based on each userdivisional in time.

Incidentally, where the radio base-station apparatus of this embodimentis used in CDMA, transmitting data is generated for each user, tocompute a transmission weight for each user. After carrying outweighting for each user, code-multiplex is implemented.

(Embodiment 2)

FIG. 5 is a block connection diagram of a radio base-station apparatusaccording to a second embodiment of the invention. In FIG. 5, powerdistributing section 207-1, 207-2, 207-N are respectively arranged closeto antenna elements 206-1, 206-2, 206-N, to distribute the power of thetransmitting signal St5-1, St5-2, St5-3 outputted from the transmittingbranch 201-1, 201-2, 201-N and output it to the correcting branch 121-1,121-2, 121-N. In this case, power distribution is slight in such adegree as not to have an effect upon the power to be fed to the antennaelement 206-1, 206-2, 206-N.

The correcting branches 121-1, 121-2, 121-N are respectively connectedto the transmitting branches 201-1, 201-2, 201-N through powerdistributing section 207-1, 207-2, 207-N. These are to feed back a partof the output from the transmitting branch, in order to compute acorrecting value. The correcting branches have the same configurationand function as that of the correcting branch 121 of FIG. 4 ofembodiment 1.

A frequency-response correcting value detecting section 214 detects afrequency characteristic of amplitude and phase deviation of thefrequency waveform data Sct4-N of from the correcting branch, on thebasis of an output signal St2-1, St2-2, St2-N of the weight operatingsection 202-1, 202-2, 202-N, thereby detecting a correcting value Ct-1,Ct-2, Ct-N to the transmitting-system radio circuit section 205-1,205-2, 205-N. In this case, the frequency-response correcting valuedetecting section 214 previously measures and stores a characteristic ofthe correcting branch radio circuit section 122-1, 122-2, 122-N of thecorrecting branch 121-1, 121-2, 121-N. By using the storedcharacteristic, the amplitude and phase deviation occurred in thecorrecting branch radio circuit section is further corrected, therebydetecting only an amplitude and phase deviation to be caused by thetransmitting branch.

The other configuration blocks and transmitting branches are the same asthose shown in embodiment 1.

Now, the operation and function is explained on the radio base-stationapparatus configured as in the above. Incidentally, because thetransmitting branches in this embodiment are all to operate in quite thesame way, explanation herein is representatively on the N-thtransmitting branch.

At first, the transmitting signal Sct1 power-distributed by the powerdistribution section 207-N is inputted to the correcting branch 121-N.

Then, the transmitting signal Sct1 is processed by the correcting branch121-N, to output frequency waveform data Sct4.

Next, the frequency waveform data Sct4-N is inputted to thefrequency-response correcting value detecting section 214. On the otherhand, the output signal St2-N of the weight operating section 202-N ofthe transmitting branch 201-N is similarly inputted to thefrequency-response correcting value detecting section 214. In thefrequency-response correcting value detecting section 214, detected is afrequency characteristic of amplitude and phase deviation of thefrequency waveform data Sct4-N of from the correcting branch 121-N, onthe basis of an output signal St2-N of the weight operating section202-N, similarly to the example shown in embodiment 1. By using this andthe already measured characteristic of the correcting branch radiocircuit section 122-N, detected is a correcting value Ct-N for thetransmitting-system radio circuit section 205 in the N-th transmittingbranch. Thereupon, previously measured and stored is a characteristic ofthe correcting branch radio circuit 122-N of the correcting branch121-N. By using the stored characteristic, previous correction is madefor the amplitude and phase deviation that is to occur in the correctingbranch radio circuit section. Thus, the detection value Ct-N is todetect only the amplitude and phase deviation caused in the transmittingbranch. Then, the correcting value Ct-N to the N-th transmitting branchdetected in the frequency-response correcting value detecting section214 is stored in the transmit correcting value memory section 112.

By providing the transmitting branches with the above configuration, itis possible to detect, concurrently in time, correcting values to thetransmitting-system radio circuit sections of the respectivetransmitting branches. Those are stored in the transmit correcting valuememory section 112.

By the above method, stored are all the correcting values to thetransmitting-system radio circuit sections 205-N of the respectivetransmitting branches.

Then, similarly to embodiment 1, the transmission weight correctingsection 113 corrects the transmission weight Wt1 computed in thetransmission weight computing section 111 by the correcting value Ctstored in the transmission correcting-value storing section 112.

Next, the transmitting signal St1 in the weight operating section 202-Nis subjected to corrected weighting, and then forwarded to the antennaelement 206-N.

By the above, directional transmission is possible in a desired beampattern through each antenna.

In this manner, according to this embodiment of the invention, it ispossible to carry out correction in a manner for always forming adesired beam pattern without communication shutdown, providing the sameeffect to the invention of embodiment 1. Efficient transmission isrealized.

Incidentally, concerning as for the signal for use in detecting acorrecting value to the transmitting-system radio circuit section,detection is possible if using any part of a transmitting signalprovided that it is a transmitting signal sent from a radio transmitterapparatus. It is possible to use a signal such as a transmitting pilotsignal sent in determined timing in time, or a transmitting data signalin communications at all times.

Incidentally, although detecting a correcting value on each transmittingbranch, correcting value accuracy can be improved by conductingdetections in plurality of number of times to take an average value intime into a correcting value.

Incidentally, although detecting a correcting value for eachsub-carrier, correcting value accuracy can be improved by utilizing acorrecting value to the adjacent sub-carrier to thereby take an averagevalue with that.

(Embodiment 3)

FIG. 6 is a block connection diagram of a radio base-station apparatusaccording to a third embodiment of the invention. In FIG. 6, a firstswitch 315 selects any one of outputs of power distribution section307-1, 307-2, 307-N according to an instruction of thefrequency-response correcting value detecting section 314. The firstswitch 315 has an output connected to a correcting branch radio circuitsection 122.

A second switch 316 is to select any one of outputs of weight operatingsections 202-1, 202-2, 202-N according to an instruction of thefrequency-response correcting value detecting section 314. The secondswitch 316 has an output connected to the frequency-response correctingvalue detecting section 314.

The other configuration blocks are the same as those shown in embodiment1 and embodiment 2.

The operation and function is explained below on the radio base-stationapparatus configured as in the above.

At first, the transmitting signals St5-1, St5-2, St5-N from thetransmitting branches 201-1, 201-2, 201-N are distributed in power bythe respective power distribution section 307, thus inputted to thefirst switch 315.

Next, the frequency-response correcting value detecting section 314instructs the first switch 315 and second switch 316, to select therespective outputs of the weight operating section andtransmitting-system radio circuit section of the same branch. Thisoperation is by an associative operation of the both switches 315, 316.The first switch 315 and the second switch 316 are the same in thetransmitting branch number to select and the timing to select.

Next, the output signal of a transmitting branch selected by the firstswitch 315 is inputted to the correcting branch 121. After undergone thesame process as that of embodiment 1 by the correcting branch 121, it isinputted to the frequency-response correcting value detecting section314. On the other hand, the output signal of a weight operating sectionin the branch selected by the second switch 316 which is the same as theselection by the first switch 315 is inputted to the frequency-responsecorrecting value detecting section 314.

Then, the frequency-response correcting value detecting section 314detects a frequency characteristic of amplitude and phase deviation ofthe output signal of from the FFT operating section 124 based on theoutput signal from the second switch 316 similarly to the embodiment 2.Then, detected is the correcting value to the characteristic of thetransmitting-system radio circuit section. The correcting value isstored to the transmit correcting value memory section 112.

The frequency-response correcting value detecting section 314 instructsthe first switch 315 and second switch 316 to detect correcting valuesas above on all the transmitting branches, and stores them in thetransmit correcting value memory section 112. The subsequent process issimilar to that of embodiment 2.

As described above, the first switch 315 and second switch 316associatively operate to switch over between the transmitting branches,whereby, even in case the correcting branch 121 is one in the number, itis possible to detect a correcting value to the transmitting-systemradio circuit section in each transmitting branch.

As described above, according to the present embodiment of theinvention, the configuration simpler than embodiment 2 can make acorrection in a manner to form a desired beam pattern at all times.Efficient transmission is realized.

Incidentally, as for the transmitting branch selecting method in thefirst switch 315 and second switch 316, the order may be previouslydetermined or may be adaptively selected. However, it is more preferableto preferentially start at a transmitting branch greater in amplitude orphase deviation in the transmitting-system radio circuit section, orincrease the detection frequency on a transmitting branch greater indeviation than that of the other branch.

Incidentally, as for the transmitting branch selecting time by the firstswitch 315 and second switch 316, the same time may be selected on thetransmitting branches or the selecting time may be changed fromtransmission branch to transmission branch.

(Embodiment 4)

FIG. 7 is a block connection diagram of a radio base-station apparatusaccording to embodiment 4 of the invention. In FIG. 7, a transmissioncorrecting matrix memory section 414 is stored with a correcting matrixMt for correcting a coupling between antenna elements. The otherconfiguration blocks are the same as those of embodiment 1. Thecorrecting matrix Mt is a matrix expressing a correcting value betweenantenna elements.

Meanwhile, the operation of the radio base-station apparatus of thisembodiment is different from that of embodiment 1 in that, in thetransmission weight correcting section 113, the transmission weight W01is corrected for a coupling between antenna elements in addition tocorrecting the characteristic of transmitting-system radio circuitsection of each transmitting branch. Namely, the transmission weightcorrecting section 113 corrects the transmission weight computed in thetransmission weight computing section 111 by multiplying a correctingmatrix stored in the transmission correcting matrix memory section 414.Also, the transmission weight correcting section 113 corrects, at thesame time, the radio circuit section of each transmitting branch by acorrecting value stored in the correcting value memory section 112.

Incidentally, there are known methods to correct mutual coupling ofantenna elements 106 described in the following documents. The documentsare “Sensor-Array Calibration Using a Maximum-Likelihood Approach” (BoonChong Ng, Chong Meng Samson See, IEEE Transactions on Antennas andPropagation, vol. 44, No.6, June 1996), “Calibration of a Smart Antennafor Carrying Out Vector Channel Sounding at 1.9 GHz” (Jean-ReneLarocque, John Litva, Jim Reilly, Wireless Personal Communications:Emerging Technologies for Enhanced Communications, p.259-268, 1999), andso on. These documents describe that a correcting matrix for correctinga coupling between antenna elements is computed and multiplied on atransmission weight thereby correcting the transmission weight. In thepresent embodiment, a correcting matrix Mt is computed by the methoddescribed in the above document and stored in the transmissioncorrecting matrix memory section 414. Herein, as explained in embodiment1, because the transmitting signal is an OFDM signal, transmissionweight can be corrected based on each sub-carrier. For this reason,sub-carrier-based correcting matrixes are computed and stored in thetransmitting correcting matrix memory section 414. Meanwhile, similarlyto embodiment 1, it is possible to divide an OFDM signal band into aplurality and gather the sub-carriers existing in the band therebycomputing and storing correcting matrixes, or to compute and store acorrecting matrix for the OFDM signal entire band.

As described above, according to the present embodiment of theinvention, the amplitude and phase deviation in the transmitting-systemradio circuit section is corrected by correcting a coupling betweenantenna elements based on each OFDM sub-carrier, in addition to whichthe affection of the interference between antenna elements can becorrected based on each sub-carrier. Due to this, a desired beam patterncan be formed within an OFDM signal bandwidth. This realizes efficienttransmission.

Incidentally, by further adding a correcting matrix memory section 414to the configuration of Embodiment 2 and 3, Embodiment 2 and 3 canobtain the similar effect to that of this embodiment.

(Embodiment 5)

FIG. 8 is a block connection diagram of a radio base-station apparatusaccording to a fifth embodiment of the invention. In FIG. 8, antennaelements 506-1, 506-2, . . . 506-N are to receive an OFDM signal from amobile station and output a signal Sr1-N. The antenna elements 506-1,506-2, . . . 506-N are in a removable arrangement.

The receiving branch 551-1, 551-2, 551-N is configured with areceiving-system radio circuit section 552-1, 552-2, . . . 552-N, ananalog/digital (A/D) converting section 553-1, 553-2, . . . 553-N, afast Fourier transform (FFT) operating section 554-1, 554-2, . . .554-N, and a weight operating section 555-1, 555-2, . . . 555-N. Herein,provided that the number of antenna elements is N, the receivingbranches are N systems. Incidentally, the function is the same among thereceiving-system radio circuit sections 552-1, 552-2, . . . 552-N,analog/digital (A/D) converting sections 553-1, 553-2, . . . 553-N, FFToperating sections 554-1, 554-2, . . . 554-N, and weight operatingsections 555-1, 555-2, . . . 555-N configuring the receiving branches551-1, 551-2, 551-N.

A reception data synthesizing section 550 is to synthesize input signalstogether.

A reception weight computing section 561 is to compute a receptionweight Wr1 from an output signal Sr4 of the FFT operating section 554 ofeach receiving branch 551. Incidentally, there are known some methods tocompute a reception weight, which are not especially limitative. Thereis, as one example, a method that a reception signal arrival directionis estimated to compute a reception weight for forming a directionalityby the utilization of the estimated direction.

A reception correcting-value memory section 562 is to store thecorrecting values Cr for correcting an amplitude and phase deviation tooccur between the receiving branches 551 on a sub-carrier-by-sub-carrierbasis.

A reception weight correcting section 563 is to correct the receptionweight Wr1 computed in the reception weight computing section 561 by acorrecting value Cr stored in the reception correcting value memorysection 562.

The operation of the radio base-station apparatus configured as above isexplained in the below.

In contrast to the radio base-station apparatus of embodiment 1 as anapparatus for sending an OFDM signal the radio base-station apparatus ofthis embodiment is an apparatus to receive an OFDM signal. Althoughthere is a difference in configuration and operation due to a change ofthe transmitting system to a receiving system, the basic object andtechnique of the invention is the same. Incidentally, operation isherein explained representatively on the N-th receiving branch.

At first, the signal Sr1-N received at the antenna element 506-N ispower-amplified by the reception-system radio circuit section, andprocessed such as by frequency conversion of from a radio frequency to abase-band frequency or intermediate frequency. Besides this, filterprocess or the like is carried out for the purpose of noise or unwantedsignal removal.

Herein, similarly to the transmission-system radio circuit section 105of embodiment 1, amplitude or phase deviation is caused between thereception branches by a characteristic difference of the analog elementsin the reception-system radio circuit sections 552.

Then, the signal Sr2-N reception-signal-processed in such radiofrequency band is converted by the A/D converter 553-N into a digitalsignal.

Next, the digital-converted signal Sr3-N, in the FFT operating section554-N, is Fourier-transformed. Herein, although there is a discreteFourier transformation or the like as a method of Fourier-transformcomputation, fast Fourier transform (FFT) is desirable in respect ofcomputation time and operation processing amount.

Then, the Fourier-transformed signal Sr4-N, in the weight operatingsection 555-N, is weighted by a reception weight Wr2 outputted from thereception weight correcting section 563. The operation of the weightoperating section 555-N is the same as the operation of the weightoperating section 102, in the embodiment 1 and weighting is made basedon each sub-carrier of OFDM signal. Due to this, outputted is a signalSr5-N weighted by the reception weight. Incidentally, the method ofcomputing a reception weight Wr2 is referred later.

The obtained output signals Sr5-1, Sr5-2, Sr5-N from the receivingbranches are inputted to the reception data synthesizing section 550 andsynthesized in the reception data synthesizing section 550, therebyobtaining received data.

Meanwhile, the foregoing reception weight Wr2 can be determined, in thereception-weight computing section 561, by correcting a reception weightWr1 computed for each sub-carrier from an output signal Sr4 of the FFToperating section of each receiving branch 551 by a sub-carrier-basedcorrecting value Cr previously stored in the reception correcting-valuememory section 562. Incidentally, because the received signal is an OFDMsignal, computing a reception weight Wr1 can be made for each carrier.Meanwhile, it is possible to divide the OFDM signal band into aplurality of bands and take the sub-carriers existing within the band asone group, thereby setting a same reception weight. This is the same asthe explanation of upon setting a transmission weight Wt in embodiment1.

Also, similarly to reception-weight computation, signal band can bedivided into a plurality of bands, to store correcting values Cr in thenumber of the divisional bands. Otherwise, sole one correcting value Crcan be stored for the entire signal band.

Herein, explained in the below is a method for determining a correctingvalue Cr.

The correcting value Cr is to detect a frequency characteristic ofamplitude/phase deviation in the receiving radio circuit section 552 andto correct the characteristic. Consequently, it is satisfactory providedthat to detect a frequency characteristic of amplitude/phase deviationin the receiving radio circuit section 552, one example of which isshown in FIG. 9. FIG. 9 is the radio base-station apparatus of thisembodiment with removal antenna elements removed and with a correctingbranch for computing a correcting value connected.

In FIG. 9, a correcting branch 571 is configured with an IFFT operatingsection 573, a D/A converting section 574 and a reception correctingbranch radio circuit section 575. The correcting branch 571 is the sameas the correcting branch 121 of embodiment 1 shown in FIG. 4.

A reference signal generating section 570 is to generate a referencesignal Scr1 for computing a correcting value.

A frequency-response correcting value detecting section 564 is to detectan amplitude and phase deviation of a signal Sr4 of from the receivingbranch 551 on each sub-carrier and compute a correcting value for eachsub-carrier, on the basis of a signal Scr1 from the reference signalgenerating section 570. The other configuration blocks are the same asthose described in FIG. 8, having the same function.

Explained is the operation of the radio base-station apparatus forcomputing a correcting value configured as above.

At first, the reference signal Scr1 from the reference signal generatingsection 570 is transmission-processed in the correcting branch 571. Thistransmission process corresponds to the process of the transmittingbranch in embodiment 1.

Then, a transmission-processed signal Scr4 is reception-processed by thereceiving branch at 551, to input an output signal Scr4 of the FFToperating section 554 to the frequency-response correcting valuedetecting section 564.

On the other hand, the signal Scr1 from the reference signal generatingsection 570 is inputted to the frequency-response correcting valuedetecting section 564.

Then, in the frequency-response correcting value detecting section 564,sub-carrier-based correcting values are computed and stored in thereception correcting value memory section 562.

By carrying out the above detection on all the receiving branches, thecorrecting values Cr for all the branches and sub-carriers can be storedin the receiving correcting value memory section.

As described above, according to the present embodiment of theinvention, by previously determining and storing an amplitude and phasedeviation to occur between the receiving branches or a correcting valuefor correcting a frequency characteristic on asub-carrier-by-sub-carrier basis, in the case to directionally send abroadband OFDM signal, it is possible to correct an amplitude and phasedeviation to occur between receiving branches and a frequencycharacteristic on a sub-carrier-by-sub-carrier basis. Due to this, adesired beam pattern can be formed within an OFDM bandwidth, enablingreception with high transmission efficiency.

Incidentally, by further adding a reception correction matrix memorysection corresponding to the transmission correcting matrix memorysection 414 storing a correcting matrix for correcting a couplingbetween antenna elements shown in FIG. 7 in embodiment 4, correction ispossible in the reception weight correcting section 563. Due to this,correction is possible for a coupling between antenna elements inaddition to correction for an amplitude and phase deviation betweenreceiving branches, enabling reception higher in transmissionefficiency.

(Embodiment 6)

FIG. 10 is a block connection diagram of a radio base-station apparatusaccording to a sixth embodiment of the invention. The radio base-stationapparatus of this embodiment is in a configuration combining togetherthe radio base-station apparatus having a transmission function ofembodiment 1 shown in FIG. 1 and the radio base-station apparatus havinga reception function of embodiment 5 shown in FIG. 8. In FIG. 10, switchsection 608-1, . . . 608-N is to switch over between a signal path offrom a transmitting branch 101-1, 101-N to an antenna element 106-1, . .. 106-N and a signal path of from the antenna element 106-1, . . . 106-Nto the transmitting branch 101-1, 101-N.

The transmission data generating section 100, the transmitting branch101-1, 101-N, the antenna element 101-1, . . . 106-N, the transmissionweight computing section 111, the transmission correcting value memorysection 112 and the transmission weight correcting section 113 are thesame as those of embodiment 1. The transmitting operation by them isalso the same.

Meanwhile, the reception data synthesizing section 550, the receivingbranches 551-1, 551-N, the reception weight computing section 561, thereception correcting value memory section 562 and the reception weightcorrecting section 563 are the same as those of embodiment 5. Thereceiving operation by those is also the same. Herein, provided that thenumber of antenna elements is N, the transmitting branches and thereceiving branches are N systems in the number.

The radio base-station apparatus configured as above is explained in thebelow.

The present embodiment has switch section provided at 608 close to eachantenna element 106, to switch over between a transmission signal offrom the transmitting branch to the antenna element and a receptionsignal of from the antenna element to the receiving branch and conveyeach of the signals, thereby combining the operations of embodiment 1and embodiment 5.

Namely, the signal from the transmitting branch 101, only when selectedto the transmitting side by each switch section 608, is conveyed only tothe antenna element 106 without being conveyed to the receiving branch551. Meanwhile, the signal from the antenna element 106, only whenselected to the receiving side by each switch section 608, is conveyedonly to the receiving branch 551 without being conveyed to thetransmitting branch at 101.

Meanwhile, in the reception weight computing section 561, a receptionweight Wr1 is computed by using a signal Sr4 that the received signal isprocessed, similarly to embodiment 5. However, in the transmissionweight computing section 111, a transmission weight Wt1 is computed byusing a reception weight Wr1 computed in the reception weight computingsection 561, differently from embodiment 1. For example, in the timedivision duplex (TDD) scheme, the reception weight Wr1 is rendered as atransmission weight Wt1 as it is while, in the frequency division duplex(FDD) scheme, receiving direction information can be estimated from areception weight Wr1 and utilized in computing a transmission weightWt1.

As in the above, according to the present embodiment of invention, wheredirectionally sending and receiving a broadband OFDM signal, bycorrecting a frequency characteristic of amplitude and phase deviationto occur between the transmitting branches and the receiving branches ona sub-carrier-by-sub-carrier basis, a desired beam pattern can be formedin an OFDM-signal bandwidth. This enables transmission and receptionwith high transmission efficiency.

Incidentally, similarly to the present embodiment, it is possible tocombine the radio base-station apparatuses of embodiments 2 and 5,combine the radio base-station apparatuses of embodiments 3 and 5, orcombine the radio base-station apparatuses of embodiments 4 and 5. Inthis case, a radio base-station apparatus can be realized which has thefunctions described in the respective embodiments.

INDUSTRIAL APPLICABILITY

As in the above, the present invention is useful for a transmitterapparatus using an array antenna for directionally sending an OFDMsignal, which is suited for obtaining a desired beam pattern even wherea frequency characteristic occurs in an amplitude/phase deviationbetween the branches.

1. A radio base-station apparatus comprising: a transmission weightcomputing section for computing a transmission weight for directionaltransmission using an OFDM signal; a transmission correcting valuememory section for storing one correcting value for correcting thetransmission weight for each sub-carrier of an OFDM signal or each bandgathering a plurality of sub-carriers; a transmitting weight correctingsection for correcting the transmission weight with the correctingvalue; and a transmitting branch for weighting transmission data with atransmission weight outputted from the transmission weight correctingsection on a sub-carrier-by-sub-carrier basis and deliver it to anantenna element.
 2. A radio base-station apparatus according to claim 1,comprising a plurality of the transmitting branches and an array antennastructured by a plurality of the antenna elements.
 3. A radiobase-station apparatus according to claim 2, wherein the transmittingbranch comprises a weight operating section for weighting thetransmission data with a transmission weight outputted from thetransmission weight correcting section, an inverse fast Fouriertransform operating section for carrying out inverse Fouriertransformation on an output signal of the weight operating section, aD/A converting section for converting an output signal of the inversefast Fourier operating section into an analog signal, and atransmitting-system radio circuit section for frequency-convert anoutput signal of the D/A converting section into a radio frequency.
 4. Aradio base-station apparatus according to claim 2, wherein thetransmission weight correcting section corrects, based on eachsub-carrier or based on each band gathering together a plurality ofsub-carriers, an OFDM-signal-sub-carrier based transmission weightcomputed in the transmission weight computing section, by using acorrecting value stored in the transmission correcting value memorysection.
 5. A radio base-station apparatus according to claim 2, whereinthe transmission weight computing section divides an OFDM signalbandwidth into a plurality and computes one transmission weight for aplurality of sub-carriers existing in a divisional band, thetransmission weight correcting section correcting, based on eachsub-carrier or based on each band gathering together a plurality ofsub-carriers, a transmission weight computed in the transmission weightcomputing section by using a correcting value stored in the transmissioncorrecting value memory section.
 6. A radio base-station apparatusaccording to claim 2, wherein the correcting value stored by thetransmission correcting value memory section is to correct an amplitudedeviation and phase deviation to occur between the transmissionbranches.
 7. A radio base-station apparatus according to claim 3,wherein the weight operating section weights transmission data on asub-carrier-by-sub-carrier basis, with a transmission weight of eachsub-carrier corrected by the transmission weight correcting section. 8.A radio base-station apparatus according to claim 3, further comprisinga correcting branch radio circuit section for inputting a signaloutputted from the transmitting branch and carrying out at leastfrequency conversion, an A/D converting section for converting an outputsignal of the correcting branch radio circuit section into a digitalsignal, a fast Fourier transform operating section forFourier-transforming an output digital signal of the A/D convertingsection, a frequency-response correcting value detecting section fortaking as a reference an output signal of the weight operating section,to detect an amplitude deviation and phase deviation of a signal of fromthe fast Fourier operating section and detect an correcting value forcorrecting an amplitude deviation and phase deviation between thetransmitting branches, the antenna element being removable.
 9. A radiobase-station apparatus according to claim 8, wherein the transmissioncorrecting value memory section is stored with a correcting valuecomputed by the frequency-response correcting value detecting sectionwhen the correcting branch radio circuit section is connected, one toone, with the transmitting branch in a state that the antenna element isnot connected.
 10. A radio base-station apparatus according to claim 3,further comprising power distributing section arranged close to theantenna element, a correcting branch radio circuit section for inputtinga signal distributed in the power distributing section and carrying outat least frequency conversion, an A/D converting section for convertingan output signal of the plurality of correcting branch radio circuitsections into a digital signal, a fast Fourier transform operatingsection for Fourier-transforming an output digital signal of the A/Dconverter section, and a frequency-response correction detecting sectionfor taking as a reference an output signal of the weight operatingsection, to detect an amplitude deviation and phase deviation of asignal of from the fast Fourier transform operating section and detect acorrecting value for correcting an amplitude deviation and phasedeviation between the transmitting branches, the transmission correctingvalue memory section being stored with a correcting value detected bythe frequency-response correction detecting section.
 11. A radiobase-station apparatus according to claim 8, wherein thefrequency-response correction detecting section detects an amplitude andphase of an output signal of the fast Fourier transform operatingsection for each sub-carrier of OFDM signal, and detects a correctingvalue for correcting an amplitude deviation and phase deviation betweentransmitting branches on a sub-carrier-by-sub-carrier basis by using adetection result of the amplitude and phase.
 12. A radio base-stationapparatus according to claim 10, wherein the frequency-responsecorrection detecting section detects an amplitude and phase of an outputsignal of the fast Fourier transform operating section based on eachsub-carrier of OFDM signal, and detects a correcting value forcorrecting an amplitude deviation and phase deviation betweentransmitting branches on a sub-carrier-by-sub-carrier basis by using adetection result of the amplitude and phase.
 13. A radio base-stationapparatus according to claim 10, further comprising a first switch forselecting one from signals distributed by a plurality of powerdistributing section and connecting it with the correcting branch radiocircuit section, a second switch for selecting a signal from a pluralityof weight operating sections and connecting it with thefrequency-response correcting value detecting section, the first switchand the second switch selecting the signal from the same transmittingbranch.
 14. A radio base-station apparatus according to claim 11,further comprising a first switch for selecting one from signalsdistributed by a plurality of power distributing section and connectingit with the correcting branch radio circuit section, a second switch forselecting a signal from a plurality of weight operating sections andconnecting it with the frequency-response correcting value detectingsection, the first switch and the second switch selecting the signalfrom the same transmitting branch.
 15. A radio base-station apparatusaccording to claim 2, further comprising a transmission correctingmatrix memory section for previously storing a correcting matrix forcorrecting a coupling between antenna elements, the transmission weightcorrecting section further correcting the transmission weight by thecorrecting matrix.
 16. A radio base-station apparatus according to claim15, wherein the transmission correcting matrix memory section is storedwith correcting matrixes based on each sub-carrier of OFDM signal.
 17. Aradio base-station apparatus according to claim 15, wherein thetransmission correcting matrix memory section is stored with correctingmatrixes based on a plurality of sub-carrier existing in plurallydevided signal bands of OFDM signal.
 18. A radio base-station apparatuscomprising: a reception weight computing section for computing areception weight by using a plurality of demodulated signal that an OFDMsignal received at an array antenna is demodulated; a receptioncorrecting value memory section for storing one correcting value forcorrecting the reception weight for each sub-carrier of an OFDM signalor each band gathering a plurality of sub-carriers; a reception weightcorrecting section for correcting the reception weight by the correctingvalue; and a weight operating section for weighting the demodulatedsignal with the corrected reception weight.
 19. A radio base-stationapparatus according to claim 18, wherein the reception weight correctingsection corrects, based on each sub-carrier or based on each bandgathering together a plurality of sub-carriers, anOFDM-signal-sub-carrier based reception weight computed in the receptionweight computing section, by using a correcting value stored in thereception correcting value memory section.
 20. A radio base-stationapparatus according to claim 18, wherein the reception weight computingsection divides an OFDM signal bandwidth into a plurality and computesone reception weight for a plurality of sub-carriers existing in adivisional band, the reception weight correcting section correcting,based on each sub-carrier or based on each band gathering together aplurality of sub-carriers, a reception weight computed in the receptionweight computing section by using a correcting value stored in thereception correcting value memory section.
 21. A radio base-stationapparatus according to claim 18, wherein the correcting value stored inthe reception correcting value memory section is to correct an amplitudedeviation and phase deviation to occur between the receiving branches.22. A radio base-station apparatus according to claim 18, wherein theweight operating section weights the demodulated signal, based on eachsub-carrier, by a reception weight of each sub-carrier corrected by thereception weight correcting section.
 23. A radio base-station apparatusaccording to claim 18 further comprising: a reference signal generatingsection for generating a signal as a reference to detect an amplitudedeviation and phase deviation between receiving branches; an inversefast Fourier transform operating section for inverseFourier-transforming a signal of from the reference signal generatingsection; a D/A converting section for converting an output signal of theinverse fast Fourier operating section into an analog signal; acorrecting branch radio circuit section for frequency-converting theoutput analog signal of the D/A converting section into a radiofrequency; and a frequency-response correcting value detecting sectionfor taking as a reference an output signal of the reference signalgenerating section, to detect an amplitude deviation and phase deviationof an output signal from the inverse fast Fourier operating section anddetect an correcting value for correcting an amplitude deviation andphase deviation between the receiving branches, the array antenna beingremovable.
 24. A radio base-station apparatus according to claim 23,wherein the reception correcting value memory section stores acorrecting value computed by the frequency-response correcting valuedetecting section when the correcting branch radio circuit section isconnected, one to one, with the receiving branch in a state that theantenna element is not connected.
 25. A radio base-station apparatuscomprising: a receiving circuit section having a receiving weightcomputing section for computing a reception weight by using a pluralityof demodulated signals an OFDM signal received at an antenna elementconfiguring an array antenna; a reception correcting value memorysection storing a correction value for correcting the reception weightbased on each sub-carrier of OFDM signal or based on band gatheringtogether a plurality of sub-carriers; a reception weight correctingsection for correcting the reception weight by the correcting value; anda weight operating section for weighting the demodulated signal by thecorrected reception weight; a transmitting circuit section having atransmission weight computing section for computing a transmissionweight for directional transmission by using information about adirectivity in the reception weight computing section; a transmissioncorrecting value memory section storing a correction value forcorrecting the transmission weight based on each sub-carrier of OFDMsignal or based on band gathering together a plurality of sub-carriers;a transmission weight correcting section for correcting the transmissionweight by the correcting value; and a transmitting branch for weightingtransmission data by a transmission weight outputted from thetransmission weight correcting section on a sub-carrier-by-sub-carrierbasis and delivering it to the antenna element; a switch section forswitching over a connection between the antenna element and thereceiving circuit section or a connection between the antenna elementand the transmitting circuit section.